/* eslint-disable */
// 当ctx传入当前文件，const grd = ctx.createCircularGradient() 和 
// const grd = this.ctx.createLinearGradient() 无效，因此只能分开处理
// 先分析，在外部创建grd，再传入使用就可以

!(function () {

    var api = {
      isGradient: function(bg) {
        if (bg && (bg.startsWith('linear') || bg.startsWith('radial'))) {
          return true;
        } 
        return false;
      },
  
      doGradient: function(bg, width, height, ctx) {
        if (bg.startsWith('linear')) {
          linearEffect(width, height, bg, ctx);
        } else if (bg.startsWith('radial')) {
          radialEffect(width, height, bg, ctx);
        }
      },
    }
  
    function analizeGrad(string) {
      const colorPercents = string.substring(0, string.length - 1).split("%,");
      const colors = [];
      const percents = [];
      for (let colorPercent of colorPercents) {
        colors.push(colorPercent.substring(0, colorPercent.lastIndexOf(" ")).trim());
        percents.push(colorPercent.substring(colorPercent.lastIndexOf(" "), colorPercent.length) / 100);
      }
      return {colors: colors, percents: percents};
    }
  
    function radialEffect(width, height, bg, ctx) {
      const colorPer = analizeGrad(bg.match(/radial-gradient\((.+)\)/)[1]);
      const grd = ctx.createCircularGradient(0, 0, width < height ? height / 2 : width / 2);
      for (let i = 0; i < colorPer.colors.length; i++) {
        grd.addColorStop(colorPer.percents[i], colorPer.colors[i]);
      }
      ctx.fillStyle = grd;
      //ctx.fillRect(-(width / 2), -(height / 2), width, height);
    }
  
    function analizeLinear(bg, width, height) {
      const direction = bg.match(/([-]?\d{1,3})deg/);
      const dir = direction && direction[1] ? parseFloat(direction[1]) : 0;
      let coordinate;
      switch (dir) {
        case 0: coordinate = [0, -height / 2, 0, height / 2]; break;
        case 90: coordinate = [width / 2, 0, -width / 2, 0]; break;
        case -90: coordinate = [-width / 2, 0, width / 2, 0]; break;
        case 180: coordinate = [0, height / 2, 0, -height / 2]; break;
        case -180: coordinate = [0, -height / 2, 0, height / 2]; break;
        default:
          let x1 = 0;
          let y1 = 0;
          let x2 = 0;
          let y2 = 0;
          if (direction[1] > 0 && direction[1] < 90) {
            x1 = (width / 2) - ((width / 2) * Math.tan((90 - direction[1]) * Math.PI * 2 / 360) - height / 2) * Math.sin(2 * (90 - direction[1]) * Math.PI * 2 / 360) / 2;
            y2 = Math.tan((90 - direction[1]) * Math.PI * 2 / 360) * x1;
            x2 = -x1;
            y1 = -y2;
          } else if (direction[1] > -180 && direction[1] < -90) {
            x1 = -(width / 2) + ((width / 2) * Math.tan((90 - direction[1]) * Math.PI * 2 / 360) - height / 2) * Math.sin(2 * (90 - direction[1]) * Math.PI * 2 / 360) / 2;
            y2 = Math.tan((90 - direction[1]) * Math.PI * 2 / 360) * x1;
            x2 = -x1;
            y1 = -y2;
          } else if (direction[1] > 90 && direction[1] < 180) {
            x1 = (width / 2) + (-(width / 2) * Math.tan((90 - direction[1]) * Math.PI * 2 / 360) - height / 2) * Math.sin(2 * (90 - direction[1]) * Math.PI * 2 / 360) / 2;
            y2 = Math.tan((90 - direction[1]) * Math.PI * 2 / 360) * x1;
            x2 = -x1;
            y1 = -y2;
          } else {
            x1 = -(width / 2) - (-(width / 2) * Math.tan((90 - direction[1]) * Math.PI * 2 / 360) - height / 2) * Math.sin(2 * (90 - direction[1]) * Math.PI * 2 / 360) / 2;
            y2 = Math.tan((90 - direction[1]) * Math.PI * 2 / 360) * x1;
            x2 = -x1;
            y1 = -y2;
          }
          coordinate = [x1, y1, x2, y2];
        break;
      }
      return coordinate;
    }
  
    function linearEffect(width, height, bg, ctx) {
      const param = analizeLinear(bg, width, height);
      const grd = ctx.createLinearGradient(param[0], param[1], param[2], param[3]);
      const content = bg.match(/linear-gradient\((.+)\)/)[1];
      const colorPer = analizeGrad(content.substring(content.indexOf(',') + 1));
      for (let i = 0; i < colorPer.colors.length; i++) {
        grd.addColorStop(colorPer.percents[i], colorPer.colors[i]);
      }
      ctx.fillStyle = grd
      //ctx.fillRect(-(width / 2), -(height / 2), width, height);
    }
  
    module.exports = { api }
  
  })();